Capacitive-sensing rotary encoder

ABSTRACT

An apparatus is provided and includes a rotary encoder that comprises a stator, a rotor, and a controller. The stator has an opening adapted to surround a first portion of a rotatable shaft, a transmit region, and a receive region. The rotor has an opening adapted to surround a second portion of the rotatable shaft, an annular conductive region, and at least one conductor electrically coupled with the annular conductive region. The controller has an input coupled to the receive region and has an output coupled to the transmit region. The controller is configured to transmit a first signal on the output of the controller and to the transmit region of the stator, receive a second signal on the input of the controller and from the receive region of the stator, and determine, based on the second signal, a proximity of the at least one conductor to the receive region.

BACKGROUND

Flow meters such as gas, water, and electric meters track an amount offluid or energy that has flowed through the meter. The meter can utilizea manual indicator such as one or more number wheels to indicate thevalue of fluid or energy used since a starting value.

SUMMARY

In accordance with one aspect, an apparatus includes a rotary encoderthat comprises a stator, a rotor, and a controller. The stator has anopening adapted to surround a first portion of a rotatable shaft, atransmit region located on a first concentric area of the stator, and areceive region located on a second concentric area of the stator. Thesecond concentric area of the stator is separate from the firstconcentric area of the stator. The rotor has an opening adapted tosurround a second portion of the rotatable shaft, an annular conductiveregion located on a first concentric area of the rotor, and at least oneconductor electrically coupled with the annular conductive region andlocated on a second concentric area of the rotor. The second concentricarea of the rotor is separate from the first concentric area of therotor. The controller has an input coupled to the receive region and hasan output coupled to the transmit region. The controller is configuredto transmit a first signal on the output of the controller and to thetransmit region of the stator, receive a second signal on the input ofthe controller and from the receive region of the stator, and determine,based on the second signal, a proximity of the at least one conductor tothe receive region.

In accordance with another aspect, an apparatus comprises a rotatableshaft, a rotor coupled to a first portion of the rotatable shaft and afixed substrate positioned adjacently to the rotor. The rotor comprisesa central region located on a first concentric area of the rotor and atleast one lobe coupled to and extending from the central region, the atleast one lobe located on a second concentric area of the rotor. Thefixed substrate has an opening surrounding the rotatable shaft, atransmit region configured to capacitively couple with the centralregion, and a capacitive sensor array configured to capacitively couplewith the at least one lobe. The apparatus also comprises a controllerelectrically coupled with the transmit region and with the capacitivesensor array and configured to receive an output from the capacitivesensor array based a signal transmitted to the transmit region anddetermine an angular rotation of the rotor based on the output.

In accordance with another aspect, a method of manufacturing a rotaryencoder comprises coupling a rotor to a rotatable shaft, positioning therotor adjacently to a stator having an opening adapted to surround asecond portion of the rotatable shaft, and coupling a controller to thetransmit region and to the receive region. The rotor has an openingadapted to surround a first portion of the rotatable shaft, an annularconductive region located on a first concentric area of the rotor, andat least one conductor electrically coupled with the annular conductiveregion and located on a second concentric area of the rotor, the secondconcentric area separate from the first concentric area, The statorcomprises a transmit region located on a first concentric area of thestator and a receive region located on a second concentric area of thestator, the second concentric area separate from the first concentricarea. The controller is configured to transmit a first signal to thetransmit region of the stator, receive a second signal from the receiveregion of the stator, and determine, based on the second signal, aproximity of the at least one conductor to the receive region.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a block diagram of an example flow meter assembly having acapacitive-sensing rotary encoder assembly in accordance with thisdisclosure.

FIG. 2 is an isometric view of a portion of an example flow meter inaccordance with this disclosure.

FIG. 3 is a schematic view of an example stator PCB in accordance withthis disclosure.

FIG. 4 is a schematic view of an example rotary PCB in accordance withthis disclosure.

FIG. 5 is a side view of an example portion of the example PCB assemblyof FIG. 1 in accordance with this disclosure.

FIG. 6 is a side view of an example portion of the example PCB assemblyof FIG. 1 in accordance with this disclosure.

FIG. 7 is a schematic view of a portion of an example flow meter inaccordance with this disclosure.

FIG. 8 is a schematic diagram of an example circuit that may be used toimplement an example sense circuit of FIG. 1 in accordance with thisdisclosure.

FIG. 9 is a schematic diagram of another example circuit that may beused to implement an example sense circuit of FIG. 1 in accordance withthis disclosure.

FIG. 10 is a schematic diagram of yet another example circuit that maybe used to implement an example sense circuit of FIG. 1 in accordancewith this disclosure.

FIG. 11 is a flow diagram of a counter decoding scheme in accordancewith this disclosure.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of an example flow meter assembly 100 havingan input 102 and an output 104. In a fluid-based flow meter, a fluidsuch as a liquid or a gas flows from the input 102 to the output 104while the flow meter assembly 100 measures the quantity of fluid passingtherethrough. Between the input 102 and the output 104, a counter driver106 is positioned in flow communication with the fluid passing throughthe flow meter assembly 100. The counter driver 106 can include amechanical conversion device to convert the fluid flowing therethroughor thereby into a rotary motion. For example, the counter driver 106 mayinclude one or more gears configured to rotate in response to the fluidflow. In an electrical energy-based flow meter, an electrical currentflowing between the input 102 and the output 104 causes anelectrical-to-mechanical counter driver 106 to convert the electricityto a mechanical motion, rotating the one or more gears as a result.

A counter assembly 108 is coupled to the counter driver 106 to visuallyindicate a running total of the quantity of fluid or energy that hasflowed through the flow meter assembly 100 since an initial value (e.g.,zero). The counter assembly 108 may include one or more number wheelsthat rotate in response to the counter driver 106. The counter assembly108 may be, for example, a decade counter having individual decimalnumber wheels having the numbers zero through nine imprinted along thecircumferential surface of each wheel. The rotation axes of the numberwheels are aligned with each other, and the wheels may be coupled in amanner that a full rotation of one wheel causes a partial rotation in anadjacent wheel. In this manner, a full rotation of a number wheel in theones place causes the number wheel in the tenths place to rotateone-tenth of a rotation to its next number. Each successive wheel iscoupled to the previous wheel in the same manner.

A capacitive-sensing rotary encoder assembly 110, in accordance withthis disclosure, is coupled to the counter assembly 108. Thecapacitive-sensing rotary encoder assembly 110 includes a printedcircuit board (PCB) assembly 112 including a rotor PCB assembly 114having a conductor 116 implemented thereon and a stator PCB assembly 118having a rotary encoder 120 implemented thereon. The rotor PCB assembly114 includes a rotor PCB for each number wheel of the counter assembly108, and each rotor PCB is configured to rotate simultaneously with itsadjacent, corresponding number wheel.

The stator PCB assembly 118 includes a stator PCB for each rotor PCB ofthe rotor PCB assembly 114. As disclosed in more detail below, as eachrotor PCB rotates relative it its corresponding stator PCB, the rotorPCB changes the capacitances of sensing capacitors of the stator PCB.

FIG. 2 is an isometric view of a portion of an example flow meter 200according to an example. A counter assembly 202 and a view panel 204 ofthe flow meter 200 are shown. Counter assembly 202 includes a pluralityof number wheels 206 arranged along a common rotation axis 208 about ashaft 210. In the illustrated example, six number wheels 206 are shown.However, more or fewer than six number wheels 206 are contemplatedherein. The six number wheels 206 may have the same markings on theouter cylindrical surface thereof or may have distinct markings on oneor more of the wheels 206. When marked with the numbers zero throughnine, the counter assembly 202 may operate as a decade counter whereeach wheel 206 rotates ten revolutions for every revolution of itsadjacent left neighbor.

A plurality of rotors 212 is attached to the plurality of number wheels206, each rotor 212 coupled to rotate with a respective wheel 206. Aplurality of stators 214 is provided, each stator 214 positionedadjacently to a respective rotor 212. A base or substrate 216 provides asupport for the stators 214. According to an example of the disclosure,the rotors 212, the stators 214, and the base 216 are constructed of oneor more PCB materials having electrical traces formed thereon.

FIG. 3 is a schematic view of an example stator PCB 300 according to anexample. Stator PCB 300 may be used to implement the example rotaryencoder 120 of FIG. 1 and includes a substrate 302 constructed of one ormore PCB materials. An opening 304 in the substrate 302 can be providedto allow a shaft or other object to extend through the substrate 302(see, e.g., FIG. 7 ).

The stator PCB 300 includes a circular capacitive sensor array 306including a number of capacitive sensing regions or receive conductors(one of which is designated at reference numeral 308 for the examplecapacitive sensing array 306) arranged about a first concentric area 310of the substrate 302. As shown, the capacitive sensing regions 308within the capacitive sensor array 306 are angularly offset or separatedfrom each other about a rotational axis 312 of the stator PCB 300 andare electrically decoupled from one another. The capacitive sensingregions 308 implement a receive region or a combined sensing capacitorfor the capacitive sensor array 306. While the number of capacitivesensing regions 308 shown in FIG. 3 provide ten sensing regions forimplementation in a decade counter, for example, the number of sensingregions 308 may include more or fewer regions to match the number ofindicators on each wheel (e.g., number wheels 206 of FIG. 2 ), which maybe more or less than ten.

The stator PCB 300 also includes a transmit region 314 arranged about asecond concentric area 316 of the substrate 302 and a ground region 318arranged about a third concentric area 320 of the substrate 302. In theillustrated example, the second concentric area 316 is closer to theopening 304 than the first concentric area 310, and the third concentricarea 320 is between both the first and second concentric areas 310, 316.However, the first and second concentric areas 310, 316 may swappositions in another example.

The transmit region 314, the ground region 318, and capacitive sensingregions 308 of the capacitive sensor array 306 may be constructed ofelectrically conductive traces, pads, and/or areas on the substrate 302such as copper or other PCB metallic trace material. Substrate 302includes a number of sensor array contact pads 322, each pad 322electrically coupled with a respective capacitive sensing region 308.Substrate 302 also includes a ground contact pad 324 electricallycoupled with the ground region 318 and includes a transmit contact pad326 electrically coupled with the transmit region 314. As illustrated,the regions 308, 314, 318 are formed on a same side of the substrate302. The pads 322, 324, 326 may further be formed on the same side asshown, or some or all may be installed on the opposite side toaccommodate trace routing or to accommodate the connector on thesubstrate 302 to which the pads 322, 324, 326 may be coupled/soldered.For example, six of the pads 322, 324, 326 shown may be formed on oneside of the substrate 302, and the remaining six may be formed on theother side of the substrate 302. Furthermore, one or more vias 328 maybe implemented to move any part of a trace to the opposite side of thesubstrate 302.

FIG. 4 is a schematic view of an example rotary PCB 400 that may be usedto implement the example rotor PCB assembly 114 of FIG. 1 . The rotaryPCB 400 includes a substrate 402 constructed of one or more PCBmaterials. An opening 404 in the substrate 402 can be provided to allowa shaft or other object to extend through the substrate 402 (see, e.g.,FIG. 7 ).

The substrate 402 has a shaped conductor member 406 formed thereon thatincludes a conductive region 408 arranged about a first concentric area410. In one example as shown, conductive region 408 is annular andsurrounds the opening 404. A pair of lobes or conductors 412, 414 of theconductor member 406 are electrically coupled with the conductive region408 and extend therefrom. The conductors 412, 414 are centrallypositioned on a second concentric area 416 and are angularly separatedand offset from each other about a central rotational axis 418 of therotary PCB 400.

In operation, the rotary PCB 400 rotates relative to the stator PCB 300.When the conductors 412, 414 overlap with respective capacitive sensingregions 308, the respective capacitive sensing regions 308 will havetheir capacitances modified due to the proximity of the conductor member406.

FIG. 5 illustrates the capacitance formed by the capacitive sensingregion 308 and ground region 318 formed on the substrate 302 of thestator PCB 300. The ground region 318 is spaced apart from thecapacitive sensing region 308 (e.g., not in physical contact, not inelectrical contact, etc.) to form an example electric field 500 when asignal is transmitted to and present on the transmit region 314. Theconductive region 408, being annular, constantly overlaps the transmitregion 314 and the ground region 318. However, the conductors 412, 414(FIG. 4 ), being alternately spaced about the second concentric area 416of the rotary PCB 400, periodically overlap any particular capacitivesensing region 308 as the rotary PCB 400 rotates about its rotationalaxis 418. In the example illustrated in FIG. 5 , none of the conductors412, 414 is rotationally positioned to overlap the capacitive sensingregion 308. Accordingly, the electric field 502 between the capacitivesensing region 308 and the ground region 318 indicates a capacitancevalue representative of no conductor 412, 414 being adjacent to thecapacitive sensing region 308. In one example, the electric field 502represents a default or baseline capacitance measurable in an initialcalibration test.

As the rotary PCB 400 rotates, the conductors 412, 414 can move into,through, and out of the electric field 502. When one of the conductors412, 414 is at least partially above or near the electric field 502(e.g., proximate to), the conductor 412, 414 interferes with theelectric field 502, thereby increasing the capacitance of the capacitivesensing region 308. FIG. 6 illustrates the capacitance formed by thecapacitive sensing region 308 and ground region 318 when one of theconductors 412, 414 is adjacent to and overlaps the capacitive sensingregion 308. As illustrated, the modified electric field 504 indicates acapacitance value experienced when the capacitive sensing region 308 andthe ground region 318 are in close proximity to one of the conductors412, 414.

The electric fields 500, 502, and 504 illustrated in FIGS. 5 and 6 areformed when a transmit signal is sent to the transmit region 314.Referring back to FIG. 2 , an integrated circuit (IC) 218 located on thebase 216, for example, includes an output 220 configured to be coupledto the transmit regions 314 of the plurality of stators 214. IC 218, asfurther described below, sends the transmit signal to the transmitregions 314 to gather capacitance values. The output 220 may include adistinct electrical connection to each transmit region 314 of theplurality of stator 214 or may be implemented in a multiplexing scheme.IC 218 further includes an input 222 coupled to the capacitive sensorarrays 306 of the plurality of stators 214. Like the output 220, theinput 222 of the IC 218 may include a distinct electrical connection toeach transmit region 314 of the plurality of stators 214 or may beimplemented in a multiplexing scheme.

View panel 204, positioned adjacently to the counter assembly 202,allows the counter assembly 202 to be visible through a portion of ahousing (not shown) into which the counter assembly 202 is placed. Anindicator 224 on the view panel 204 may be aligned with the plurality ofnumber wheels 206 to visibly indicate the number value of the counterassembly 202.

FIG. 7 illustrates a schematic view of portion of an example flow meterassembly 700 in accordance with this disclosure. As illustrated, threenumber wheel assemblies 702, 704, 706 are assembled together in acounter assembly 708. The number wheel 710 of number wheel assembly 702is fixedly coupled to a rotary PCB 712, and one or both of the numberwheel 710 and the rotary PCB 712 are fixedly coupled to a shaft 714passing therethrough. Accordingly, the number wheel 710, shaft 714, androtary PCB 712 rotate in unison. Number wheel assemblies 704, 706 alsoinclude respective number wheels 716, 718 fixedly coupled to respectiverotary PCBs 720, 722 so that rotation of the number wheel 716 causes thesame rotation in the rotary PCB 720 and that rotation of the numberwheel assembly 718 causes the same rotation in the rotary PCB 722. Thenumber wheels 716, 718 also include passages or apertures (not shown)formed therein to allow the shaft 714 to pass therethrough. However,unlike the number wheel assembly 702, the number wheels 716, 718 are notfixedly attached to the shaft 714 but are allowed to rotateindependently thereof.

A counter driver 724 coupled to the shaft 714 causes the shaft 714 andthe number wheel 710 and rotary PCB 712 attached thereto to rotate basedon the flow of a fluid or energy through the flow meter assembly 700. Aflow-to-rotation assembly 726 may be directly coupled to the shaft 714or may be coupled via a gear assembly 728, for example. The counterdriver 724 is designed to convert the fluid or energy flow into arotation movement that causes the shaft 714 and, therefore, the firstnumber wheel 710 to rotate. The number wheel 710 includes a gearengagement member 730 configured to cause partial rotation of a gear 732positioned adjacently to the first and second number wheels 710, 716.Rotation of the gear 732 causes partial rotation of the number wheel716. Accordingly, each rotation of the number wheel 710 causes a partialrotation in the number wheel 716 via the gear 732. According to oneexample, ten rotations of the number wheel 710 causes a full rotation ofthe number wheel 716. Similarly, a gear engagement member 734 on thenumber wheel 716 engages a gear 736 positioned adjacently to the secondand third number wheels 716, 718. According to the example providedherein, ten rotations of the number wheel 716 causes a full rotation ofthe number wheel 718.

Each number wheel assembly 702, 704, 706 also includes a respectivestator PCB 738, 740, 742, each coupled to a substrate 744 having thereonan IC 746 configured to determine the angular rotation of the numberwheels 710, 716, 718 based on determining a plurality of capacitancevalues experienced by the stator PCBs 738, 740, 742. The stator PCBs738, 740, 742 may also include openings such as opening 304 (FIG. 3 ) toallow the shaft 714 to pass therethrough. Additionally, openings (notshown) formed to allow gears 732, 736 and their common shaft 748 to passtherethrough may be formed depending on the arrangement.

FIG. 8 is a schematic diagram of an example sense circuit 800 for acombined sensing capacitor 802 for a capacitive sensor array 306 in theform of an oscillator circuit. The example sense circuit 800 may be usedto implement an example sense circuit embedded within or otherwiseaccessible to the IC 218. When a control input 804 is set to a logichigh (e.g., equal to a supply voltage Vcc), an example resistor laddernetwork 806 creates an example reference input 808 for an examplecomparator 810 that changes with an example output 812 of the comparator810. The example reference input 808 toggles and has a polarity that isopposite the charge and discharge of the capacitive sensor 802. In theexample of FIG. 8 , if the resistors R of the resistor ladder network806 have approximately equal resistances, then the oscillation or cyclefrequency f_(OSC) of the output 812 of the comparator 810 can beexpressed mathematically as:f _(osc)=1/(1.386R _(C) C _(SENSOR)),where C_(SENSOR) is the capacitance of the capacitive sensor 802, whichvaries responsive to the proximity of a conductor, such as the exampleconductor member 406. As discussed above in connection with FIGS. 3-6 ,as a conductor interferes with the electric field 502, 504, thecapacitance of the capacitive sensor 804 increases and, thus, the cyclefrequency f_(OSC) of the output 812 of the comparator 810 increases.That is, the cycle frequency f_(OSC) can be used as a measure of thecapacitance of the capacitive sensor 802.

To determine (e.g., estimate, measure, etc.) the cycle frequency f_(OSC)of the output signal 812 of the comparator 810, the example sensecircuit 800 includes an example counter 820 and the example countregister 830. The example counter 820 counts cycles of the output signal812 by, for example, counting rising or falling edges of the output 812.At periodic intervals, the current cycle count is stored in the examplecount register 830 for subsequent retrieval, and the counter 820 isreset. The larger the count stored in the count register 830, the higherthe cycle frequency f_(OSC) of the output 812, and the larger thecapacitance of the capacitive sensor 802, which indicates a largerinterference of the capacitive sensor 802 by a conductor.

FIG. 9 is a schematic diagram of another example sense circuit 900 for acombined sensing capacitor 902 for a capacitive sensor array 306 in theform of a charge-transfer circuit. The example sense circuit 900 of FIG.9 may be used to implement an example sense circuit embedded within orotherwise accessible to the IC 218. In FIG. 9 , a resistor-capacitor(RC) network 904 is used to charge a circuit voltage 906. Charge isperiodically transferred from the sense capacitor 902 to the RC network904 by controlling with a signal 908 which controls example switches SW₁and SW₂. When a conductor is proximate to the capacitive sensor 902, thecapacitance of the capacitive sensor 902 increases, and more charge istransferred from the capacitive sensor 902 to the RC network 904 percycle of the signal 908. By counting, with a counter 910, the number ofcycles of the signal 908 needed for the circuit voltage 906 to exceed athreshold voltage V_(REF), a measure of the capacitance of thecapacitive sensor 902 can be determined. At periodic intervals, thecurrent count is stored in an example count register 912 for subsequentretrieval, and the counter 910 is reset. The smaller the count stored inthe count register 902, the larger the capacitance of the capacitivesensor 904, which indicates a larger interference of the capacitivesensor 904 by a conductor.

FIG. 10 is a schematic diagram of yet another example sense 1000 for acombined sensing capacitor 1002 for a capacitive sensor array 306 in theform of a sigma-delta sense circuit. The example sense circuit 1000 ofFIG. 10 may be used to implement an example sense circuit embeddedwithin or otherwise accessible to the IC 218. In FIG. 10 , thecapacitive sensor 1002 charges a resistor-capacitor (RC) network 1004that charges a circuit voltage 1006. When a conductor is proximate tothe capacitive sensor 1002, the capacitance of the capacitive sensor1002 increases, and charge is transferred faster from the capacitivesensor 1002 to the circuit voltage 1006. Once the circuit voltage 1006exceeds a threshold reference voltage V_(REF), a comparator 1008 istripped, and discharge of the circuit voltage 1006 through a resistor1010 begins. As the capacitance of the capacitive sensor 1002 increases,the discharging slows as charging by the capacitive sensor 1002continues. Counting, with a counter 1012, the number of cycles of anoutput signal 1014 of an oscillator 1016 until discharging completes,the capacitance of the capacitive sensor 1002 can be determined. Atperiodic intervals, the current count is stored in an example countregister 1018 for subsequent retrieval, and the counter 1012 is reset.The larger the count stored in the count register 1018, the larger thecapacitance of the capacitive sensor 1002, which indicates a largerinterference of the capacitive sensor 1002 by a conductor.

FIG. 11 is a flow diagram of a counter decoding scheme 1100 executableby a microcontroller or IC (e.g., IC 218 of FIG. 2 ) according to anexample. Counter decoding scheme 1100 can be executed to determine thenumber value of a counter assembly (e.g., counter assembly 108, 202, 708of FIGS. 1,2, 7 ) with one or more number wheels. The IC readscalibration parameters (step 1102) from a set of calibrations parametersstored on a computer-readable memory storage device. The calibrationparameters may include a lookup table and have default capacitancevalues for each capacitive sensing region of each stator PCB (e.g.,capacitive sensing region 308 of stator PCB 300 of FIG. 3 ) of thecounter assembly. The calibration parameters may be measured and storedduring the manufacturing process for the counter assembly, for example,and may include sensed capacitance values for each capacitive sensingregion when the rotor conductors (e.g., conductors 412, 414 of FIG. 4 )are not overlapping the capacitive sensing region. In addition, thecalibration parameters may include sensed capacitance values for eachcapacitive sensing region when one or both rotor conductors respectivelyoverlap the capacitive sensing region. In this manner, a default orbaseline capacitance value for each capacitive sensing region may bestored and used for normalization during the counter decoding scheme1100 as described below.

The first wheel to be decoded (“decoding wheel”) is set (step 1104) andmay be a most-significant-digit wheel (e.g., the wheel in the thousandsplace in a three-digit counter), a least-significant-digit (e.g., thewheel in the ones place in a three-digit counter), or any wheel inbetween. For the decoding wheel to be decoded, the respective statorcorresponding to the decoding wheel is used to acquire capacitance valuemeasurements from its capacitive sensor array. Scheme 1100 enables (step1106) the transmit (“TX”) pin on the stator for the decoding wheel bytransmitting a voltage signal from the IC executing the scheme 1100 tothe transmit region of the stator. Capacitance measurements are acquired(step 1108) from each capacitive sensing region (e.g., capacitivesensing regions 308 of FIG. 3 ) on the stator. The capacitancemeasurements may include determining the capacitance value on eachcapacitive sensing region as described, for example, in FIGS. 8-10 .

Each of the acquired capacitance measurements is normalized (step 1110)based on the calibration parameters. Normalization may include finding adifference between the recently measured capacitance value and thecalibrated capacitance value from the calibration parameters. Thecapacitance measurements are analyzed to identify (step 1112) thelargest capacitance value or values. The number of lobes (e.g.,conductors) of the conductor member of the rotor indicates the number oflarge capacitance values that may be identified. In one example, for theembodiments described herein where the dual-lobed conductor member 406includes the two conductors 412, 414, two largest values may beidentified.

The angular rotation or position of the rotor is determined (step 1114)based on the largest identified capacitance value(s). When the rotor hasa single conductor lobe, the angular rotation or position of the rotorcan be determined to correspond with the position of the capacitivesensing region that sensed the largest value. When the rotor hasmultiple conductor lobes, multiple capacitive sensing regions senselarge capacitance values. In this case, the angular rotation or positionof the rotor can be determined based on the angular offset of thecapacitive sensing regions that sensed the large values correlated withthe angular offset of the multiple conductor lobes. When fixed to arotating shaft (e.g., shaft 210 of FIG. 2 ), determination of theangular rotation or position of the rotor is correlated to the angularrotation or position of the shaft. In one example, when the rotor isrotated so that the first conductor (e.g., conductor 412) is alignedwith the first capacitive sensing region and the second conductor (e.g.,conductor 414) is aligned with the fourth capacitive sensing region, theangle of rotation of the rotor may be known to be a certain value suchas 0 degrees. When the first conductor is aligned with the secondcapacitive sensing region and the second conductor is aligned with thefifth capacitive sensing region, for example, the angle of rotation ofthe rotor may be known to be 36 degrees. Other rotation angles of therotor may be likewise known.

A correlation exists between the rotation angle of the rotor and thenumbers or symbols on the corresponding decoding wheel based on whichnumber or symbol is indicated when the decoding wheel is rotated to aparticular position. Since the rotation of the rotor matches therotation of the number wheel, determining (step 1116) the wheel value ofthe decoding wheel includes decoding the number or other symbol on theface of the wheel that is lined up with, for example, a visual indicator(e.g., indicator 224 of FIG. 2 ) based on the angular rotation orposition of the number wheel. For example, if the angular position ofthe rotor is an angle of 0 degrees, a corresponding angular position ofthe number wheel at 0 degrees may correspond with a number value of“zero”. Similarly, if the angular position of the rotor is an angle of180 degrees, a corresponding angular position of the number wheel at 180degrees may correspond with a number value of “five”.

Counter decoding scheme 1100 determines (step 1118) whether additionalwheels remain to be decoded. If so (1120), the decoding wheel is set(step 1122) to the next wheel to be decoded, and execution returns tostep 1106 to decode the next wheel.

If no additional wheels are left to decode (1124), counter decodingscheme 1100 can append all the decoded numbers and determine whether theresulting counter number is reasonable (step 1126). For example, if thecounter number is less than a previously decoded number based on acomparison of the current number to a historical log, it may bedetermined that the current value is not reasonable in an example wherea larger number is expected. If the current number is not reasonable(1128), execution of scheme 1100 may return to step 1104 to reevaluateall wheels of the counter assembly. However, if the counter number isreasonable (1130), the counter number value may be recorded (step 1132)into the historical log or other memory location. The counter decodingscheme 1100 may then end (step 1134).

The foregoing description of various preferred embodiments of theinvention have been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The example embodiments, as described above, were chosen anddescribed in order to best explain the principles of the invention andits practical application to thereby enable others skilled in the art tobest utilize the invention in various embodiments and with variousmodifications as are suited to the particular use contemplated. It isintended that the scope of the invention be defined by the claimsappended hereto.

What is claimed is:
 1. An apparatus comprising: a rotary encodercomprising: a stator having an opening adapted to surround a firstportion of a rotatable shaft, the stator further comprising: a transmitregion located on a first concentric area of the stator; and a receiveregion located on a second concentric area of the stator, the secondconcentric area separate from the first concentric area; a rotor havingan opening adapted to surround a second portion of the rotatable shaft,the rotor further comprising; an annular conductive region located on afirst concentric area of the rotor; and at least one conductorelectrically coupled with the annular conductive region and located on asecond concentric area of the rotor, the second concentric area separatefrom the first concentric area; and a controller having an input coupledto the receive region and having an output coupled to the transmitregion, wherein the controller is configured to: transmit a first signalon the output of the controller and to the transmit region of thestator; receive a second signal on the input of the controller and fromthe receive region of the stator; and determine, based on the secondsignal, a proximity of the at least one conductor to the receive region.2. The apparatus of claim 1, wherein the controller is configured todetermine a rotational position of the rotatable shaft based on theproximity of the at least one conductor to the receive region.
 3. Theapparatus of claim 2, wherein the second signal indicates a capacitancebetween the at least one conductor of the rotor and the receive regionof the stator.
 4. The apparatus of claim 1, wherein the receive regionof the stator comprises a capacitive sensor array.
 5. The apparatus ofclaim 1, wherein the first concentric area of the stator is closer tothe opening of the stator than the second concentric area of the stator.6. The apparatus of claim 5, wherein the stator further comprises aground region located on a third concentric area positioned between thefirst concentric area of the stator and the second concentric area ofthe stator.
 7. The apparatus of claim 5, wherein the first concentricarea of the stator is configured to overlap the first concentric area ofthe rotor; and wherein the second concentric area of the stator isconfigured to overlap the second concentric area of the rotor.
 8. Theapparatus of claim 1, wherein the at least one conductor of the rotorcomprises: a first conductor; and a second conductor angularly offsetfrom the first conductor about a rotational axis of the rotor.
 9. Theapparatus of claim 8, wherein the receive region of the stator furthercomprises a plurality of receive conductors, each receive conductor ofthe plurality of receive conductors independently coupled with thecontroller and angularly offset from each other about a centralconcentric axis of the stator; and wherein, when the first conductor ispositioned adjacently to a first receive conductor of the plurality ofreceive conductors and the second conductor is positioned adjacently toa second receive conductor of the plurality of receive conductors, atleast a third receive conductor of the plurality of receive conductorsis positioned between the first and second receive conductors, along ashortest angular distance between the first and second receiveconductors.
 10. An apparatus comprising: a rotatable shaft; a rotorcoupled to a first portion of the rotatable shaft and comprising: acentral region located on a first concentric area of the rotor; and atleast one lobe coupled to and extending from the central region, the atleast one lobe located on a second concentric area of the rotor; a fixedsubstrate positioned adjacently to the rotor and having an openingsurrounding the rotatable shaft, the fixed substrate comprising: atransmit region configured to capacitively couple with the centralregion; and a capacitive sensor array configured to capacitively couplewith the at least one lobe; and a controller electrically coupled withthe transmit region and with the capacitive sensor array and configuredto: receive an output from the capacitive sensor array based a signaltransmitted to the transmit region; and determine an angular rotation ofthe rotor based on the output.
 11. The apparatus of claim 10, wherein asubstrate of the rotor comprises printed circuit board (PCB) material;and wherein the capacitive sensor array comprises copper formed on asurface of the PCB material.
 12. The apparatus of claim 10, wherein thecapacitive sensor array comprises a plurality of receive conductorsarranged about a first concentric area of the fixed substrate; andwherein the transmit region is arranged about a second concentric areaof the fixed substrate.
 13. The apparatus of claim 12, wherein thecontroller, in being configured to determine the angular rotation, isconfigured to: determine a capacitance value between each receiveconductor of the plurality of receive conductors and the rotor;correlate at least one receive conductor of the plurality of receiveconductors with the at least one lobe based on the determinedcapacitance values; and determine the angular rotation of the rotorbased on an angular position of the at least one receive conductor andan angular position of the at least one lobe.
 14. The apparatus of claim13, wherein the controller is further configured to: acquire acalibration parameter for the at least one receive conductor from a setof calibration parameters; and determine a difference between thecalibration parameter and the output from the capacitive sensor.
 15. Theapparatus of claim 12 further comprising: a number wheel coupled to therotor; and a flow meter configured to allow an amount of one of a fluidand an energy to flow therethrough and to rotate the number wheel basedon the amount flowing through the flow meter.
 16. The apparatus of claim15, wherein the flow meter further comprises an indicator aligned withthe number wheel; and wherein the controller, in being configured todetermine the angular rotation, is configured to: determine acapacitance value between each receive conductor of the plurality ofreceive conductors and the rotor; correlate at least one receiveconductor of the plurality of receive conductors with the at least onelobe based on the determined capacitance values; determine the angularrotation of the rotor based on an angular position of the at least onereceive conductor and an angular position of the at least one lobe; andcorrelate the angular rotation of the rotor with a number value of thenumber wheel aligned with the indicator.
 17. A controller configured to:transmit a first signal to a transmit region of a stator, wherein thetransmit region is located on a first concentric area of the stator;receive a second signal from a receive region of the stator, wherein:the receive region is located on a second concentric area of the stator;the second signal is based on an interaction of the first signal with aconductor member formed on a rotor positioned adjacently to the stator;and wherein the conductor member comprises at least one conductor lobe;and determine, based on the second signal, a proximity of the at leastone conductor lobe to the receive region.
 18. The controller of claim17, wherein the controller, in being configured to determine theproximity of the at least one conductor lobe to the receive region, isconfigured to determine a capacitance between the at least one conductorlobe and the receive region.
 19. The controller of claim 18, wherein thereceive region comprises a plurality of receive conductors arrangedabout the first concentric area; and wherein the controller, in beingconfigured to determine a capacitance between the at least one conductorlobe and the receive region, is configured to: determine a capacitancevalue between each receive conductor of the plurality of receiveconductors and the conductor member; and correlate at least one receiveconductor of the plurality of receive conductors with the at least oneconductor lobe based on the determined capacitance values.
 20. Thecontroller of claim 19, wherein the controller is further configured todetermine an angular rotation of the rotor based on an angular positionof the correlated at least one receive conductor.